Interpretive Summary: Corn stover, the aboveground material left in fields after corn grain harvest, has been identified as a potential feedstock to help supply biofuel needed to offset a portion of the 14 million barrels of oils consumed daily by the U.S. transportation sector. This study reports on the organizational structure and initial soil quality assessment made as part of a multilocation project to determine the impact of harvesting crop residue on several soil quality indicators. The soil qualilty assessment using the Soil Management Assessment Framework (SMAF) shows that total organic carbon is the soil quality indicator that needs to be monitored most closely to quantify crop residue removal effects on the soil resource. This information will be of value to conservationists, research scientists, the Natural Resources Conservation Service personnel, the Department of Energy, and entrepreurers developing sustainable biomass harvest strategies for the bioenergy industry.

Technical Abstract:
Harvesting feedstock for advanced biofuel production must not degrade soil, water, or air resources. Our objective of this report is to provide an overview of field research being conducted in six states to quantify effects of harvesting corn (Zea mays L.) stover as a potential bioenergy feedstock. Coordinated field studies were initiated near Ames, IA; St. Paul and Morris, MN; Mead, NE; University Park, PA; Florence, S.C.; and Brookings, S.D., as part of the USDA-ARS Renewable Energy Assessment Project (REAP). A baseline soil quality assessment was made using the Soil Management Assessment Framework (SMAF). Corn grain and stover yield for two different cutting heights (50% and 100%) were measured at all sites. Although currently available soil data from these sites is still quite limited, an initial Soil Management Assessment Framework (SMAF) analysis indicated that total organic carbon (TOC) is a soil quality indicator that needs to be closely monitored to quantify crop residue removal effects. Overall, grain yields averaged 9.7 and 11.7 Mg ha-1 (155 and 186 bu ac-1) in 2008 and 2009, values that are consistent with national averages for both years. The average amount of stover collected for the 50% treatment was 2.6 and 4.2 Mg ha-1 for 2008 and 2009, while the 100% treatment resulted in an average removal of 5.4 and 7.4 Mg ha-1, respectively. Based on a recent literature review, the removal rates for both harvest scenarios could result in a gradual decline in TOC. However, the literature value has a large standard error, so continuation of this long-term multi-location study for several years is warranted.